Python’s built-in hasattr(object, string) function takes an object and a string as an input. It returns True if one of the object‘s attributes has the name given by the string. Otherwise, it returns False.
Table of Contents
Usage
Learn by example! Here’s an example on how to use the hasattr() built-in function.
# Define class with one attribute
class Car:
def __init__(self, brand):
self.brand = brand
# Create object
porsche = Car('porsche')
# Check if porsche has attributes
print('Porsche has attribute "brand": ', hasattr(porsche, 'brand'))
print('Porsche has attribute "color": ', hasattr(porsche, 'color'))
The output of this code snippet is:
Porsche has attribute "brand": True Porsche has attribute "color": False
It has the attribute “brand” but not the attribute “color”.
Video hasattr()
Syntax hasattr()
The hasattr() object has the following syntax:
Syntax:
hasattr(object, attribute) # Does the object have this attribute?
| Arguments | object | The object from which the attribute value should be drawn. |
attribute | The attribute name as a string. | |
| Return Value | object | Returns Boolean whether the attribute string is the name of one of the object‘s attributes. |
Return value from hasattr()
The hasattr(object, attribute) method returns True, if the object has the attribute and False otherwise.
Interactive Shell Exercise: Understanding hasattr()
Consider the following interactive code:
Exercise: Fix the code so that both results of hasattr() return True!
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Applications hasattr()
- You can use
hasattr()to avoid accessing errors when trying to access an attribute of a dynamic object. - You can use
hasattr()in a ternary operator to conditionally assign a value to a variable such as in:age = object.age if hasattr(object, 'age') else 0 - However, be careful when using
hasattr()as it always returnFalse, no matter the error message. Thus, it may overshadow an error different to the error that appears if the attribute doesn’t exist. So, the attribute may indeed exist but if trying to access it causes an error, the result will beFalse.
Related Functions
- The
getattr()function returns the value of an attribute. - The
setattr()function changes the value of an attribute. - The
hasattr()function checks if an attribute exists. - The
delattr()function deletes an existing attribute.
Summary
Python’s built-in hasattr(object, string) function takes an object and a string as an input.
- It returns
Trueif one of theobject‘s attributes has the name given bystring. - It returns
Falseotherwise if one of theobject‘s attributes doesn’t have the name given bystring.
>>> hasattr('hello', 'count')
True
>>> hasattr('hello', 'xxx')
False
Note that hasattr() also returns True if the string is the name of a method rather than an attribute.
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